Three-way, 2-position DCVs are used to power actuators in one direction.

• A. Control actuator speed
• B. Power actuators in one direction
• C. Power actuators in both directions
• D. Stop actuators in any position

Answer: (B)

The idea being tested is how a three-way, two-position directional control valve behaves with an actuator. This type of valve has three ports: supply, an output to the actuator, and an exhaust. In one position, supply pressure is connected to the actuator, pushing it in a single direction. In the other position, that actuator port is connected to exhaust, venting the air and allowing the actuator to return (usually aided by a spring or the load). Because there isn’t a path that directs pressure to drive the actuator in the opposite direction, these valves are used to power actuators in one direction only. This setup is common with single-acting cylinders, where extending the piston requires pressurized air and retraction occurs passively or via a return spring.

Speed control isn’t the primary role of this valve; flow affects how quickly the actuator extends, but the main function is unidirectional actuation. For bidirectional control, a four-way (or 5/2) valve is used. It also doesn’t inherently lock the actuator in any arbitrary position—the action is either pressurize or vent, with holding depend­ing on the system design (such as springs or external restraints).